Electric resistance alloy



, We July 2 UNITED STATES 'PXTEN T oFFicE" 2,288,660 ELECTRIC RESISTANCEALLOY Hans Gustaf Albert you Kantzow and Bengt Gunnar Oscar Nordstriim,

Sweden Hallstahammar,

No Drawing. Application June 30, 1939, Serial i In Sweden February 25,1938 4 Claims.- (Cl. 201-76) In electric resistance materials for hightemperatures, which in addition to-iron contain as main ingredientschromium, aluminium and cobalt as well as possibly titanium, it has beenfound that the strength of the material at high temperatures is notsumcient when the resistance materials are used for certainconstructions, for

example, types of radiating apparatus. This is substantially due to thefact that at high temperatures (for example 1000-1250" C.) the materialundergoes a permanent elongation. which will remain after the materialhas cooled down. An object of the present invention is to overcome thisdisadvantage and thus to improve the strength at high temperatures ofthe alloys of the above types used as resistance materials and which, inaddition to iron, contain as main ingredients chromium in the proportionof 15-35%,

aluminium 1-'7% and cobalt 0.5-8%, in which the cobalt may partly bereplaced by titanium.

The said improvement is obtained by adding to such alloys certainingredients which can into the 'alloys in the proportion of 0.24% and0.1-4% respectively, and columbium in the proportion of 0.1-3%.

By one or several of the additions mentioned an increase in the strengthof the material at high temperatures is obtained without its resistanceto oxidation, and thus its life, being decreased. It has been found,however, that by means of additions of molybdenum and/or tungsten thematerial becomes somewhat more brittle, thus reducing its possibilitiesof being worked and increasing the percentage of scrap during themanufacturing process. If, however, columbium is present in conjunctionwith molybdenum and/ or tungsten the columbium will restore wholly or inpart the tenacity that the material would have had without an additionof the ingredients mentioned.

In order further to increase the strength of the material and especiallywith a View to obtaining the largest possible number of crystallisationcentres with the accompanying finer grain distribution a gas which isinert to carbon, for example, nitrogen, can be blown into the moltenmetal bath. On account of the vigorous stirring that takes place anextremely fine dispersion of nitrides is produced in the bath, which canserve as a basis for the production of crystals.

Below a few examples, are given of suitable compositions of steel alloysproduced accordin to the present invention. The proportions areexpressed as percentages the remainder being iron.

I II III IV V VI VII VIII IX Cr. 24 25.8 26 27 18 27. 2 28 26. 2 19 A]4.5 4.7 5 5 4.0 5.3 6 5 5.5 Go... 3 3 1.5 2.5 1.5 4.5 2.8 2.0 Ti 0.8M0..-" 1.0 0.4 1 0.2 1.1 W 0.7 12 0.6 05 0 0.6 1.2 1.0 0.6 Cb 0.7 0.50.7 1.0 0.7 0.0

The carbon content should be kept as low as possible, but can varybetween 0.01-0.3% up to about 0.5%.

Inaddition to the main ingredients mentioned the alloys can containmanganese and silicon in the proportions used for steel, as well as oneor more secondary ingredients which occur as impurities in thecrudematerial such as sulphur, or which can'be added to the alloysduring the manufacturing process, for example, those derived from theslag used or from the lining of the furnace.

We claim:

1. An electric resistance alloy capable of withstanding hightemperatures of substantially the following composition: carbon fromabout 0.01 to 0.3 per cent, chromium from about 19 to 35 per cent,aluminum from about 1 to 7 per cent, cobalt from about 0.5 to 8 percent, columbium from about 0.1 to 3 per cent and a small amount withinthe range of about 0.1 to 4 per cent of at least one of the metalsselected from the group consisting of molybdenum, tungsten and titanium,the balance of said composition being substantially iron.

2. An electric resistance alloy capable of withstanding hightemperatures of substantially the following composition: carbon fromabout 0.01 to 0.3 per cent, chromium from about 19 to 35 per cent,aluminum from about 1 to 7 per cent, cobalt from about 0.5 to 8 percent, columbium from about 0.1 to 3 per cent and molybdenum from about0.1 to 4 per cent, the balance of said composition being substantiallyiron.

3. An electric resistance alloy capable of withstanding hightemperatures of substantially the followingcomposition: carbon fromabout 0.01 to 0.3 per cent, chromium from about 19 to 35 per cent,aluminum from about 1 to 7 per cent, c0-

balt from about 0.5 to 8 per cent, columbium Tmmabout; 0.1115. 3 ercent, molybdenum from about 0.1 to 4 per cent, titanium from about 0.5

to 4 per cent and tungsten from about 0.2 to 3 per. cent, the balance ofsaid composition bein! 5 substantially iron.

4 HANS GUSTAF ALBERT VON KANTZOW. BENGT GU'N'N'AR OSCAR NORDSTRbM

